Stator winding for a transverse flux machine and method for the production of a stator winding

ABSTRACT

The invention relates to a stator winding for a transversal flow machine, the stator winding (98) being embodied as a cord (244) and said cord (244) having a plurality of individual wires (242). Said stator winding (98) is embodied as a coil with several windings (245), characterized in that one or more windings (245) are layered in the axial direction or radial direction.

BACKGROUND OF THE INVENTION

The design of a transverse flux machine is known from the dissertation“Entwicklung and Optimierung einer fertigungsgerechtenTransversalflussmaschine” [Development and optimization of a transverseflux machine suitable for manufacture], author Mr. Michael Bork,Shaker-Verlag, publication year 1997, in particular page 78 et seq.therein.

Said document proposes the use of a stator winding comprising a litzwire.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the method according to the invention as wellas a control apparatus and a system with a control apparatus and a startapparatus are illustrated in the drawings, in which:

FIG. 1 shows a longitudinal section through a first embodiment of anelectric machine,

FIG. 2 shows a front view of an electric machine on a flange withoutelectronics,

FIG. 3 shows a three-dimensional view of the machine shown in FIG. 2,

FIG. 4 shows a three-dimensional view of the machine shown in FIG. 1,

FIG. 5 shows a rear view of the electric machine on a flange withdismantled electronics,

FIG. 6A shows a longitudinal section through the stator,

FIG. 6B shows a detail of the stator shown in FIG. 6A,

FIG. 7 shows a three-dimensional view of the stator,

FIG. 8 shows a further three-dimensional view of the stator shown inFIG. 7,

FIG. 9 shows a fan,

FIG. 10 shows a view into a cavity of an external rotor,

FIG. 11 shows two views of the external rotor with an external viewbeing illustrated in the upper half of the picture and a longitudinalsection view being illustrated in the lower half of the picture,

FIG. 12 shows a three-dimensional view of a stator winding,

FIG. 13A shows a cross section through the stator winding,

FIGS. 13B and 13C show further possible cross sections through thestator winding,

FIG. 14 shows a cross section through a wire of a litz wire,

FIG. 15 shows a further cross section through the stator winding,

FIG. 16 shows a detail of the stator winding,

FIGS. 17a ) to g) show various method steps for producing a statorwinding,

FIGS. 18a ) to e) show two different stator windings, different methodsteps for producing a stator winding and two different cross sectionsthrough the stator windings,

FIG. 19 shows three connection parts of the stator windings which arestar-connected,

FIG. 20 shows a variant of a stator,

FIG. 21 shows a second embodiment of an electric machine with theconfiguration of a transverse flux machine.

DETAILED DESCRIPTION

FIG. 1 illustrates an electric machine with the configuration of atransverse flux machine 10. As is the case for many electric machines,this electric machine also has a stator 13 and a rotor, in the form of aso-called external rotor 16. Both parts are arranged in a housing 19.The external rotor 16 is driven by means of a shaft 22. In this case,the shaft 22 is driven by means of a pulley or a gearwheel or anothertorque transmission part. Electronics 28, for example a passiverectifier or an active rectifier, are arranged beneath a cover 25 on theleft-hand side in FIG. 1.

An approximately pot-shaped housing shell 34, which has a ring-shapedcollar 37 with a central opening 40, is supported on a flange 31. Theshaft 22 extends through the opening 40.

Furthermore, the stator 13 is also supported on the flange 31. Thestator 13 is fastened indirectly to the flange 31 by means of sevenscrews 43. The screws 43 protrude through in each case onethrough-opening in the flange 31 and engage in in each case one threadedbore 46 of a further flange 49. This further flange 49 is integrallyconnected to a central sleeve 52, which likewise performs central tasks.

The sleeve 52 bears, over its inner contour 54, two rolling bearings 55and 56, which in this case are in the form of deep groove ball bearings.The inner contour 54 has two ring webs 59 and 60. The ring web 60 servesas a stop for the rolling bearing 56. Between the ring web 59 and therolling bearing 55, in order to produce an axial prestress on the tworolling bearings 55 and 56, a disk spring 57 is clamped between the ringweb 59 and the rolling bearing 55. The shaft 22 is mounted fixed inposition and rotatably via these rolling bearings 55 and 56. The shaft22 is placed between the bearing seats for the rolling bearings 55 and56. A spacer sleeve 63 is pushed onto the shaft 22 between the tworolling bearings 55 and 56, in order that a defined distance is setbetween the rolling bearings 55 and 56. The two rolling bearings 55 and56, or their inner rings (not illustrated here in any more detail), arebraced with one another and against a shoulder 69 by means of the spacersleeve 63, a tensioning sleeve 66 and a tensioning screw 67. An outerring 70 of the rolling bearing 56 is secured in position by an innersecuring ring 71.

The shoulder 69 also has the task of protecting the rolling bearings 55and 56, as well as the task of forming a stop for the external rotor 16.The external rotor 16 has a pot-like configuration. A section 73 in theform of a cylinder lateral surface of the external rotor 16 bearspermanent magnets 77 on its cylindrical inner side 75 in three rowsarranged axially successively. A type of housing base 80, which restswith a central bore 83 on the shaft 22, adjoins the section 73 in theform of a cylinder lateral surface of the external rotor 16, extendingradially inwards at an axial end. A radially acting fan 86 is fastenedon an inner side of the housing base 80. A further fan 89, which is inthe form of a narrow ring in the radial direction, is fastened on thesection 73 in the form of a cylinder lateral surface which is directedtowards the electronics 28. This fan 89 rotates in a groove which isincorporated in a front side of the flange 31 which is directed towardsthe fan 89. Radially outside this fan 89, a series of ventilationopenings 90 is arranged all the way round in the housing shell 34.

The stator 13 is arranged radially within the section 73 in the form ofa cylinder lateral surface. This stator 13 comprises three individualspecial ring systems 92. Each ring system 92 has two half-rings 94 and96, which, between them, accommodate a ring coil as stator winding 98.The stator winding 98 is surrounded or encompassed in each case by twohalf-yokes 100 and 101, two ring walls 102 and 103 and claw poles 104and 105; see also FIG. 6A. The claw poles 104 and 105 in this casealternate with one another in the circumferential direction. In thiscase, an accommodating area 106 for the stator winding 98 is formed. Theaccommodating area 106 has a specific cross section, delimited by thehalf-yokes 100 and 101, the two ring walls 102 and 103 and the clawpoles 104 and 105. The stator winding 98 with a preformed cross sectionrests in this accommodating area 106, which is rectangular in thisexample. The cross section of the stator winding 98 is matched to thecross section of the accommodating area 106.

Arranged in concentrated fashion, three outputs 108, 109 and 110 of thein total three stator windings 98 are located radially inside the stator13, i.e. between the half-yokes 100 and 101, which in total make up aninner yoke 107, and the sleeve 52. Each output 108, 109 and 110 is inthis case associated with a stator winding 98. The three stator windings98 are star-connected to one another, which will be discussed in moredetail further below.

Ventilation channels 113, which are part of a ventilation system whichwill likewise be described in more detail below, are located radiallyinside the stator 13, i.e. likewise between the half-yokes 100 and 101and the sleeve 52.

FIG. 2 shows a front view of the electric machine on the flange 31 withdismantled electronics. The flange 31 has a through-hole 115 for arespective fastening eyelet 114 at the clock positions “half one”, “sixo'clock” and “half ten”. These through-holes 115 are preferably equippedwith internal threads 116, as illustrated here, and are used forfastening the electric machine to its surroundings. Six furtherthrough-holes 118, of which in each case two times two through-holes 118are arranged in the fastening eyelets 114 and in each case onethrough-hole 118 is arranged in individual fastening eyelets 119, areused for fastening the housing shell 34 to the flange 31. For thispurpose, correspondingly six tie rods 121, in the form of long screws(see also FIG. 3), are plugged through further through-holes 122, whichare incorporated in ring segments 123. By virtue of applying asufficient torque to the tie rods 121, the housing shell 34 is heldreliably in position on the flange 31.

Three threaded bores 125 located at the clock positions “two o'clock”,“six o'clock” and “ten o'clock” are used for fastening a cooling plate127 (illustrated by way of example in FIG. 1) by means of screws 130.The cooling plate 127 itself serves to cool the electronics 28.

Five of the seven screws 43 protrude into a groove 133 in the form of aring segment, which extends approximately 270° about an axis of rotation136. Four slots 142 which are likewise in the form of ring segmentsprotrude from a base 139 of the groove 133, through which slots a viewof the claw poles 104 and 105 and a casting compound 144 is free. Thecasting compound 144 covers the stator windings 98. A ring-shaped web147 delimits the flange 31 radially inwards and delimits a circularcentral through-opening 149 radially outwards. Inlet openings of theventilation channels 113 are illustrated radially within the web 147. Inthe background, fan blades 152 of the fan 86 can be seen through theventilation channels 113.

In the foreground at the “twelve o'clock” position, three connectinglugs 155 with cable sleeves 156 are illustrated. These connecting lugs155 serve the purpose of making contact with the three stator windings98 (see also FIG. 3). In this example, three-phase current can beunderstood as a specific form of an alternating current. In contrast tothe illustration in FIG. 1, the current of the three stator windings 98can be guided by means of the connecting lugs 155 to so-called“path-building” electronics (for example a passive rectifier or anactive rectifier), which are not arranged on the cooling plate 127.

The individual ventilation channels 113 are separated by radial webs158. These webs 158 protruding from the inner yoke 107 act as coolingribs, cool the stator 13 and extend from the inner yoke 107 radiallyinwards. These webs 158 or cooling ribs are integrally formed on theinner yoke 107. The webs 158 shown directly in FIG. 2 are moreover webs158 which are incorporated in the flange 49. The same arrangement ofwebs 158 and ventilation channels 113 is also implemented in thehalf-rings 94 and 96. While the flange 49 merges with a tubular section160 of the sleeve 52 after the webs 158, when viewed radially from theoutside, the webs 158 of the half-rings 94 and 96 merge with a thin ringregion 162. The webs 158 or cooling ribs which are spaced apart in thecircumferential direction are connected integrally to one anotherradially on the inside by the ring region 162. In the axial direction, aplurality of ring regions 162 a plurality of half-rings 94, 96 arebraced with one another.

FIG. 3 shows the abovementioned ventilation openings 90 over the outercircumference of the housing shell 34. Furthermore, a fan blade 164 ofthe fan 89 is shown within the ventilation openings 90, in a mannerrepresentative of the entire fan 89.

Against the background of FIG. 1, FIG. 4 shows the technical solutionwith built-on electronics. Thus, the current produced by the outputs108, 109, 110 is conducted via three conductor rails 166, 167 and 168 tothe connections 169, 170. A third connection is provided, but this isnot illustrated in FIG. 4 because it is hidden by the conductor rail167. Protruding from the cover 25, a positive connection 173, forexample for supplying power to a power supply system of a motor vehicle(not illustrated) is shown.

In addition, the connecting lugs 155 can also be fastened at the outputs108, 109, 110.

FIG. 5 shows a rear view of the electric machine on the flange 31 withthe electronics 28 dismantled or not fitted and also without the housingshell 34 and without the shaft 22 fitted. It can clearly be seen thatthe webs 158 are integrally formed on the half-ring 96. The same alsoapplies to the other half-ring 94. This integral formation of thisstructure comprising the webs 158 and the ventilation channels 113 withthe ring region 162 is technically less complex when the material fromwhich the half-rings 94 and 96 are manufactured is a so-calledferromagnetic powder composite material (SMC, i.e. “soft magneticcomposite”). In view of the fact that this material is at present verycostly, the structures comprising the webs 158 and the ventilationchannels 113 can be produced in a less complex manner, which will bediscussed in more detail further below.

As can already be seen from FIG. 1, the half-rings 94 and 96 are pushedonto the sleeve 52 with the stator windings 98 until they hit againstthe flange 49. The half-rings 94 and 96 are in this case centered by arecess 176 (FIG. 6A). By virtue of two different form-fitting elementsin the form of knobs 179 and corresponding depressions 180, thehalf-rings 94 and 96 are centered with respect to one another. Apressure and centering ring 182 firstly results in an assemblycomprising the half-rings 94 and 96 being centered around the sleeve 52and a compressive force (generated by a tightened shaft nut 184) isapplied to the SMC material without or virtually without a transverseforce. A corresponding transverse force would be transmitted to the SMCmaterial if the shaft nut 184 were to transmit the frictional forceproduced by it being tightened between itself and a body to be clampeddirectly to the SMC material.

The rolling bearing 56 is inserted into the sleeve and secured by theinner securing ring 71. The flange 31 has a recess 186 in the outer edgeregion on that side of said flange which is directed towards the stator13. This recess 186 serves the purpose of centering a housing shell 34(FIGS. 5 and 6A).

On its side directed towards the viewer, i.e. on the side pointing awayfrom the flange 31, the half-ring 96 has a groove 189. This grooveserves the purpose of being able to allow the casting compound 144 toflow between the two radial sides of the half-rings 94 and 96. FIG. 6Bshows a detail, in this case a section through two half-rings 94 and 96.As can be seen in said figure, the two half-rings 94 and 96 have a notch190 and 191, respectively, whose profiles run radially inwards, are atright angles and supplement one another to form, overall, a rectangularoverall profile. Special connecting parts of the stator winding 98 runin these notches 190 and 191. Owing to the corresponding similarity, allof the half-rings 94 and 96 have a notch 190 and 191, respectively.

FIG. 7 shows a three-dimensional view of the stator 13. As can alreadybe seen from FIG. 5, the half-rings 94 and 96 have a further notch 194,at which there are no webs 158. The outputs 108, 109 and 110 are guidedaxially in the region of or in this notch 194 (see also FIG. 1 and FIG.6A).

The claw poles 104 and 105 of each ring system 92 engage alternately inclaw pole gaps 196 and claw pole gaps 198, respectively, between therespective other claw poles. The claw pole gaps 196 are between clawpoles 104, and the claw pole gaps 198 are between the claw poles 105. Ascan be seen from FIG. 7, a claw pole 104 of a ring system 92 bearsagainst a claw pole 105 of another ring system 92. The claw poles 104and 105 of the three ring systems 92 are in this case arranged in such away that undulating paths 200 and helical paths 201 are produced betweenthe claw poles 104 and 105. These paths 200 and 201 serve the purpose ofallowing cooling air to pass through.

FIG. 8 shows a further three-dimensional view of the stator 13. Thethree connections 108, 109, 110 of the three stator windings 98 extendthrough an opening 203 in the flange 49 of the sleeve 52. In each caseone insulating layer 205 or 206, which is produced from a polyamidefilm, for example, is located between the three connections 108, 109,110, i.e. between the connection 108 and 109 and between the connection109 and 110. As is also apparent in this regard from FIG. 1, functionalsections of the connections 108, 109, 110 are of different lengths:measured from the first end face 209, which is directed towards theflange 31, those parts or sections of the connections 108, 109, 110which are directed towards the stator windings 98 have approximately aratio of 1:2:3 with respect to one another. That is to say that thecorresponding section of the connection 108 is only approximately athird as long as the corresponding section of the connection 110. On theother hand, those sections of the connections 108, 109, 110 which aredirected towards the electronics 28 have a different ratio with respectto one another, for reasons of space. Thus, the lengths of the sectionsof the connections 108, 109, 110 from the end face 211 illustrated inFIG. 6A is approximately 3:5:3. That is to say that the section of thecentral connection 109 protrudes beyond the two other sections of thetwo other connections 108 and 110.

The insulating layer 205 extends at least from the outermost end face213 of the connection 108, said end face 213 pointing away from thestator 13, as far as at least the outermost end face 215 of theconnection 109, said end face 215 pointing away from the end face 213 ofthe connection 108.

In more general terms, the insulating layer 205 extends between twodirectly adjacent connections 108 and 109 at least over the length whichis between two end faces 213 and 215 pointing away from one another.

The insulating layer 206 extends at least from the outermost end face218 of the connection 110, said end face 218 pointing away from thestator 13, as far as at least the outermost end face 220 of theconnection 110, said end face 220 pointing away from the end face 218 ofthe connection 110.

In more general terms, the insulating layer 206 extends on or at theconnection 110, which makes contact with the stator winding 98, which isfurthest removed from the end face 209 of the ring system 92, which ispositioned closest to a connection side 217 of the stator 13, over atleast the entire axial length of the connection 110.

The three or the connections 108, 109, 110 are provided with athrough-hole 224 on the side pointing away from the stator windings 98at a point 222 which overall overlaps with respect to the connections108, 109 and 110. The insulating layers 205 and 206 are likewiseperforated at this point 222. A sleeve 225 consisting of an insulatingmaterial is plugged into the five holes. This sleeve 225 protrudesbeyond the structure comprising the connections 108, 109, 110 andinsulating layers 205 and 206 on both sides; see inter alia FIG. 6A andFIG. 8. The conductor rail 168 which is centered by the sleeve 225 restson the upper side of this structure, i.e. on the connection 108; theconductor rail 166 centered by the sleeve 225 rests on the lower side ofthis structure, i.e. on the connection 110 (FIG. 1 and FIG. 4). Twoinsulating disks 227 resting thereon form bottom layers or top layersfor a fastening means such as, for example, a screw and a nut, which arenot illustrated here and press the structure with high contactstability.

FIG. 9 illustrates the fan 86 illustrated in FIG. 1 as an individualpart in a three-dimensional view. This fan 86 is fastened on the innerside of the housing base 80 of the external rotor 16 by means of a fewfastening elements. The fan 86 has a central opening 230, whose diameteris greater than an outer diameter of the shaft nut 184 (FIG. 1).

FIG. 10 shows a view into the cavity of the external rotor 16. Theillustration clearly shows the fan blades 152 of the fan 86 and innerends of the fan blades 164 of the fan 89, which are prevented frombending radially outwards by a stabilizing ring 233. The external rotor16 is constructed from various component parts (see also FIG. 11): thehousing base 80 is pressed against the shoulder 69 of the shaft 22. Inthe process, a screw 234 which is screwed into a shaft end presses asleeve 235 against a stabilizing plate 237, which in turn transmits thecompressive force onto the housing base 80. In order that the shaft 22,the plate 237 and the housing base 80 can be fitted in the correctposition with respect to one another, dowel pins 238 are inserted intobores in the shoulder 69. The housing base 80, the plate 237 and thesleeve 235 are positioned onto these dowel pins 238.

The permanent magnets 77 are fastened on the substantially cylindricalinner side. The fan 89, which is produced from plastic, for example, isplugged on at that end 240 of the section 73 in the form of a cylinderlateral surface which is remote from the housing base 80, by means of asnap-action connection. For this purpose, a ring section 243 which isintegrally formed on the fan 89 engages around the cylindrical outerside of the section 73 in the form of a cylinder lateral surface.

FIG. 12 shows a three-dimensional view of a stator winding 98, in thiscase the stator winding 98 which is positioned closest to the connectionside 217. The stator winding 98 comprises precisely one turn 245.However, the stator winding 98 is in this case in the form of a litzwire 244, the litz wire 244 having a plurality of individual wires 242(FIG. 13A). In accordance with a specific design, provision is made forthe litz wire 244 to have 1000 wires with a diameter of in each case 0.2mm. All of the individual wires 242 of the litz wire 244 are thus woundonce (slightly less than 360°, i.e. not quite 360°). The individualwires 242, i.e. each individual wire cross section consisting of copper,for example, of the litz wire 244 can be insulated with respect to oneanother by a layer of enamel as insulating layer 247, as shown in FIG.14. Then, the litz wire 244 is additionally insulated at its outercircumference, with this being performed by banding 249, for example.The litz wire 244 is first prepared in linear form. The individual wires242 of the litz wire 244 are then all next to one another linearly. Ifit were then desired to wind such a linear banded litz wire 244, thiswould result in considerable non-uniform changes in length and internalstresses (between the individual wires) over the cross section of thelitz wire 244. Alternatively, as shown in FIG. 13A, the individual wires242 of the litz wire 244 can also be embodied without insulation 247.Then, the possible disadvantage of relatively high current displacementstands against the possible advantage of relatively high copper crosssection. In the exemplary embodiment described here, the litz wire 244has a current displacement of 1.14 at 10 000 revolutions per minute.

Following this step, the litz wire 244 is circumferentially compressedin the region of an intended abutment (the two ends of the litz wire 244are opposite one another there) and the litz wire 244 is provided withtwo straight end faces. In the region of said end faces, the insulatinglayer 247 is removed and the wires are connected to one another by asolder. The stator winding 98 now has an open circular ring form ofapproximately 360°, with the stator winding 98 having two mutuallyopposite ends 250, 251, the end 251 with a connection part 108 and theend 250 with a connection part 253 (eyelet connection) being cohesivelyconnected to one another. In this case, an end 250, 251 is connected toa connection part 108, 253 in such a way that a rim 254 of a connectionpart 108, 253 surrounds the end (FIG. 16). The connection part 108, 253is in this case pressed against the end 250, 251 while a solder for thecohesive connection is still fluid. Furthermore, an insulating material256, for example an insulating plate, is introduced between theconnection part 108 and the connection part 253 (eyelet connection) inorder that no short circuit is produced between the connection part 108and the eyelet connection 253. Then, the stator winding 98 is banded.Preferably, in the process a neck section 258 is also banded. This necksection 258 comprises, both of the connection part 108 and theconnection part 253 (eyelet connection), in each case one section whichprotrudes radially inwards. This neck section 258 protrudes into thenotches 190 and 191 in the fitted machine (see also FIG. 6B).

As part of the production method, a plurality of method steps areprovided. First, a litz wire 244 is provided (FIG. 17a )). In a furtherstep, the litz wire 244 is compacted, i.e. the litz wire 244 is providedapproximately with a cross section which corresponds to the statorwinding 98 (FIG. 17b )). By way of example, three different form crosssections after compacting or embossing of the litz wire 244 areillustrated in FIG. 17b ). During this method step, bundling of the litzwire 244 is expedient (possibly even by means of possibly only onebanding) in order to avoid any movement of the wires, in particular inthe following winding step. In FIG. 17c ) below, further embodiments ofthe litz wire 244 are illustrated, in which not only the actual turnsection is embossed, but also both ends 246 which extend in addition inthe axial direction. While FIG. 17c ) shows a litz wire 244 with a roundcross section, the litz wire in FIG. 17d ) has a rectangular crosssection. FIG. 17e ) illustrates a litz wire 244 or stator winding 98which has been embossed with a rectangular form, with two laminations248 as connections having been soldered or welded onto a radial outerside or the two ends 246 of the litz wire 244. FIG. 17f ) illustrates alitz wire 244 or stator winding 98 which has been embossed with arectangular form, with two laminations 248 as connections having beensoldered or welded onto a radial inner side or the two ends 246 of thelitz wire 244. FIG. 17g ) illustrates a litz wire 244 or stator winding98 which has been embossed with a rectangular form, with two laminations248 as connections having been soldered or welded onto a radial outerside or the two ends 246 of the litz wire 244. In this case, the litzwire 244 has been embossed in advance in such a way that a notch hasbeen embossed into the annular cross section of the stator winding 98,with the laminations 248 having been fitted into said notch.

With reference to FIG. 13A, in the exemplary embodiment a stator winding98 has an unbanded cross section A1 with a radial height H in thedirection towards an axis of rotation of the external rotor 16 and anaxial width B in the direction of the axis of rotation of the externalrotor 16. In the example, B is approximately 10 mm and H isapproximately 7 mm. The unbanded cross section is thereforeapproximately 70 mm². An individual wire of the litz wire 244 has across section A2 of 0.1²*Πmm² and therefore approximately 0.0314 mm². Aratio A1/A2 is in this case approximately 2228. In the context of thedesign of the stator winding 98, provision is made for the ratio in afirst approximation to be less than 2500, and in a further approximationto be less than 2000 or less than 1500.

As a further ratio, a quotient of the cross section A1 and acircumference U of an individual wire of the litz wire 244 can bedetermined. A quotient A1/U of approximately 111 mm results from theexample, where U is equal to the product of Π*0.2 mm. In a firstapproximation, it is desirable for the ratio A1/U to be greater than 40,and in a second approximation greater than 80, preferably greater than120. FIG. 13B illustrates an alternative cross-sectional form for thestator winding 98. This cross-sectional form is a total area (“housewith pitched roof” form) comprising a rectangle as in FIG. 13A and atriangle on top. The triangle represents a gain with respect to thecross-sectional form in FIG. 13A resulting from optimized matching ofthe accommodating area radially beneath the claw poles 104 and 105. InFIG. 13C, a trapezoid is provided as further cross-sectional form of thestator winding 98 as a basic shape, with the sloping faces beingoriented substantially in the axial direction. In addition, thetrapezoidal form can in total be supplemented by a triangularcross-sectional area beneath the claw poles 104 and 105.

A further exemplary embodiment of a stator winding 98 is shown in FIG.18a ). This stator winding 98, in contrast to the previously describedvariant, is a stator winding 98 comprising a litz wire 244 with morethan only one turn 245. This has the advantage that the currentdisplacement is further reduced. Furthermore, greater flexibility asregards the matching of the number of conductors in the stator winding98 is provided. In addition, optimum use can be made of the so-calledwinding window. As already described in respect of FIG. 17a ), first awinding phase of litz wire 244 comprising a large number of insulatedindividual wires 242 (FIG. 14) is provided. This winding phase is theninsulated, for example by means of banding 249 (FIG. 13A). The windingphase is arranged in a plurality of turns 245 prior to or after theinsulation is provided (see also FIG. 18a ) and FIG. 18b )) (forms inring form, further exemplary embodiment). In FIG. 18a ), the turns 245are wound or layered radially (axially in FIG. 18b )) one on top of theother. FIG. 18c ) is a schematic illustration showing individual steps.In step S1, the insulated litz wire 244 is first compressed in order toflatten the litz wire 244 (axial direction); preferably an innerdiameter of the stator winding 98 or the litz wire 244 is alreadypreset. Then, the flattened litz wire 244 is shaped (step S2); possiblynot only an outer diameter but also the inner diameter is adjusted orshaped. Then, the stator winding 98 or the litz wire 244 is embossed,with the result that the width B is also set (step S3). Possibly, in afurther step S4, a fixed structure is then produced, i.e. the statorwinding 98 or the litz wire 244 is coated or impregnated with apreferably thermally curable resin (baked enamel), possibly heated in aform and thus a solid stator winding 98 is produced.

FIG. 18d ) shows a possible cross section through the stator winding 98or the litz wire 244, as is illustrated by the winding process shown inFIG. 18a ) and is produced after compacting or embossing.

FIG. 18e ) shows a possible cross section through the stator winding 98or the litz wire 244, as is illustrated by the winding process shown inFIG. 18b ) and is produced after compacting or embossing.

A stator winding 98 for a transverse flux machine 10 is thereforedisclosed, wherein the stator winding 98 is in the form of a litz wire244 and the litz wire 244 has a plurality of individual wires 242, thestator winding 98 being in the form of a coil with more than one turn245. Finally, prior to or following curing, connections are fitted tothe stator winding 98 in one of the described ways.

A method for producing a stator winding 98 comprising a litz wire 244 isthus disclosed, wherein first a litz wire strand is provided and, inlater steps S1, S2, S3, the stator winding 98 is shaped into a ringform, insulated and a cross section of the stator winding is reshaped.Provision is made for more than only one turn to 245 to be wound in acircumferential direction.

Provision is furthermore made for the stator winding 98 to be coatedwith a curable material, preferably resin or baked enamel, and later forthis material to be cured.

FIG. 19 illustrates three connection parts 253 of the three statorwindings 98 arranged one after the other. In this case, these connectionparts are the parts which act as eyelet connection. The three connectionparts 253 are spaced apart from one another. In each case one metal bush260 is located between two connection parts 253. A screw bolt 262 of ascrew 264 is plugged through the connection parts 253 and the bushes260. The connection parts 253 and the bushes 260 are braced with oneanother, with the result that an electrical connection is providedbetween connection parts 253 and bushes 260. This arrangement is theneutral point of the three stator windings 98. A transverse flux machineis therefore disclosed, wherein in each case one of the connections ofthe stator windings 98 has a hole 263 and these connections or one ofthe connection parts 253 of the stator windings 98 are arranged axiallyone behind the other in the direction of rotation of an external rotor16, these connection parts 253 being mechanically and electricallyconnected to one another by a bolt (screw bolt 262) positioned in theholes 263 and a neutral point thus being formed. Against the backgroundof a generalization: this arrangement, either so as to form the neutralpoint or so as to pass out the connections 108, 109 and 110, isindependent of the selection of the embodiment of the stator winding 98.It is merely important that, in order to form the neutral point, one endof a stator winding 98 is embodied with a connection part 253, withpreferably all of the stator windings 98 being embodied in such a way.In order to pass out the connections 108, 109 and 110 or to arrange saidconnections with respect to one another, provision is merely made forone end of the stator windings 98 to be connected to one of theconnections 108, 109 and 110.

The text which follows will describe the cooling of the transverse fluxmachine 10, which is described in FIGS. 1 and 4 (with attachedelectronics). By virtue of a rotation of the external rotor 16 andtherefore also of the fan 86, a negative pressure is produced in themachine. This negative pressure results in air being transportedradially outwards through the fan 86, i.e. between the housing base 80and the half-ring 96 of the ring system 92, which is positioned closestto the housing base 80. This cooling air is deflected by the externalrotor 16 and, as shown in FIG. 7, is pressed between the claw poles 104and 105 and therefore into an interspace 265 in the axial direction. Thecooling air flows around all of the three ring systems 92 and is thenpressed by the fan 89 radially outwards through the ventilation openings90 into the surrounding environment.

The negative pressure produced by the fan 86 means that a negativepressure is produced at that end of the ventilation channel 113 which isdirectly opposite the fan 86 and therefore cooling air then flowsthrough the ventilation channel 113. At that end of the ventilationchannel(s) 113, which is remote from the fan 86, cooling air is suckedfrom the surrounding environment, for example in the region of theconnections 108, 109 and 110, through the flange 31 and thereforethrough the through-opening 149 (FIG. 4). In addition, cooling air issucked into the machine through openings 270 in the cover 25 in orderfirst to cool the electronics 28 and then to flow through openings (notshown in FIG. 1) in the cooling plate 127 to the through-opening 149(FIG. 2) and into the ventilation channels 113. In addition, the fan 89sucks additional cooling air for cooling the electronics 28 through theslots 142 and the groove 133 and openings (not shown) in the coolingplate 127.

A transverse flux machine 10 with a stator 13 and an external rotor 16,which is arranged around the stator 13, is thus disclosed, the stator 13having two axial end sides 273, 276 remote from one another, with aninner yoke 107 of the stator 13, with a cooling path which is arrangedradially within the inner yoke 107, the cooling path emerging from thetransverse flux machine 10 on that axial end side 273 of the stator 13which faces the inlet side, the cooling path running between the inletand the outlet in an interspace between the stator 13 and the externalrotor 16.

FIG. 20 shows a detail of a view of a variant of the stator 13. Incontrast to the previous variant, the half-rings 94, 96 are delimitedradially inwards by the inner yoke 107, i.e. the half-rings 94, 96 donot have any webs 158. Instead, the half-rings 94, 96 have a central,preferably round opening 279. A cooling rib element 280 consisting of aless expensive material such as an aluminum alloy, for example, isinserted into this opening 279, i.e. adjacent to the inner yoke 107,said cooling rib element 280 enabling heat emission from the half-rings94, 96 by means of cooling ribs 283 and enabling centering of thehalf-rings 94, 96, preferably by means of an inner ring 285, on thesleeve 52. The cooling rib element 280 can be an extruded profile, forexample.

FIG. 21 shows a sketch of a further exemplary embodiment of a transverseflux machine 10. Identically functioning component parts are denoted bythe same reference numerals. Thus, a three-phase stator 13 with threering systems 92 is fastened on a housing inner wall 290 on a housing 19.A shaft 22 is mounted both in the housing 19 and radially within thestator 13, for which purpose the rolling bearings 55 and 56 are used. Asupporting plate 293 is fastened with concomitant rotation on that endof the shaft 22 which is remote from the housing inner wall 290. Thissupporting plate 293 bears fan blades 152 radially and axially on theoutside. A section 73 in the form of a cylinder ring is mounted on thatside of the supporting plate which is opposite the fan blades 152. Aswas previously the case, permanent magnets 77 are likewise fastened inthree rows on the cylindrical inner side of said section 73, saidpermanent magnets magnetizing the ring systems 92 with their magneticfield. An end plate 296 between the shaft 22 and fan blades 152 servesto improve the fan efficiency. By virtue of rotation of the shaft, forexample by means of a pulley (not illustrated) at the left-hand end ofthe shaft 22, the fan 86 brings about a negative pressure at the outeredge of the fan 86. A draught of air or cooling air is thus producedthrough the machine, said draught being described by the two longarrows, beginning at the cooling air inlet 300. The cooling airtherefore moves first from an inlet side 303 on one side of the stator13 radially inwards in order to be deflected there in the axialdirection (axis of rotation of the external rotor 16). Then, the coolingair flows past webs 158 in the axial direction in the interior of thestator 13. Then, the cooling air emerges from that side of the stator 13which is remote from the inlet side in order to be deflected radiallyoutwards and to be passed out of the machine by the fan blades 152.

A transverse flux machine with a stator 13 and an external rotor 16which is arranged around the stator 13 is thus disclosed, the stator 13having two axial end sides 273, 276, with an inner yoke 107 of thestator 13, with a cooling path, which is arranged radially within theinner yoke 107, the cooling path emerging from the transverse fluxmachine 10 on that axial end side 273 of the stator 13 which is remotefrom an inlet side 303.

What is claimed is:
 1. A method for producing a stator winding for atransverse flux machine, the method comprising: providing a litz wirewinding phase of the stator winding, wherein the litz wire winding phaseincludes a plurality of individual wires (242), and wherein theindividual wires (242) are not insulated with respect to one another;shaping the litz wire winding phase into a ring form; insulating thelitz wire winding phase, after shaping the litz wire winding phase;reforming a cross section of the litz wire winding phase, afterinsulating the litz wire winding phase; and winding more than only oneturn (245) of litz wire winding phase in a circumferential direction,the more than one turn (245) being layered in one of an axial directionand a radial direction.
 2. The method as claimed in claim 1, furthercomprising coating the stator winding with a curable resin, and curingthe resin.
 3. The method as claimed in claim 1, wherein the more thanone turn (245) is layered in the axial direction.
 4. The method asclaimed in claim 1, wherein the more than one turn (245) is layered inthe radial direction.